Introduction

The antenatal diagnosis of lethal, short-limbed dyssegmental dysplasia of the Silverman-Handmaker type has recently been reported by our institution.1 Dyssegmental dysplasia is characterized by marked disorganization of the vertebral bodies, bowing of the long bones (camptomelia) and micromelia. Other findings may include cephalocele, mid-facial defects, cleft palate, cardiac defects, and hydronephrosis. Inheritance is probably autosomal reces­sive. Patients of Hispanic origin seem to be heavily represent­ed in the Silverman-Handmaker variety of the disease.1

At our institution we have recently diagnosed and delivered another patient with the Silverman- Handmaker type of dyssegmental dysplasia.

Case report

The patient is an 18 year old unmarried female of Hispanic/German origin. She presented to the antenatal testing unit at our institution at seventeen weeks estima­ted gestational age. She was a referral from her primary care physician for evaluation of “intrauterine growth retardation.”

Ultrasonographic findings at this time included marked disorganization of the vertebral bodies, a shortened femur demonstrating camptomelia, and a posterior cephalocele (fig. 1-2).

Fig. 1: Ultrasound of the femur demonstrating marked bowing of the diaphysis (camptomelia). Right: Ultrasonographic demonstration of disorganization of the spinal column. Note the haphazard arrangement of the vertebral bodies in the lumbar region.

The diagnosis of dyssegmental dysplasia was made, and the patient was offered genetic counseling. She was counseled that this disease is always lethal and was offered pregnancy termination. She declined and opted to continue the pregnancy.

Further history revealed no substance abuse, exposure to toxins, or family history of consanguinity. Serial ultrasounds were performed throughout the gestation and revealed hydronephrosis in addition to the previously mentioned findings. Two days subsequent to the last ultrasound at 36 weeks of gestational age, the patient reported no fetal movement. An intrauterine fetal demise was confirmed. The patient was indu­ced and delivered a stillborn female infant weighing 1720g.

Fig. 4: Radiograph at autopsy demonstrating marked disorganization of the vertebral bodies. See text for further description of bony deformities.

Radiographic find­ings at autopsy demonstrated marked vertebral disorganization, short humeri, and femurs with splayed metaphyses. Also noted was abnormal angulation of the bones of the distal extremities (fig. 3 right).

Comments

The antenatal diagnosis of short-limbed dwarfism is usually made in one of two clinical situations: the patient is referred for ultra­sound secondary to a family history of dwarfism, or routine exam reveals a femur measuring less than the 5th percentile for gestational age. Rhizomelic dwarfism is characterized by shortening of proximal long bones; micromelic dwarfism, exemplified by dyssegmental dysplasia, reveals abnormalities in all bony structures.

Izquierdo1, Aleck2, and others have described the typical findings of dyssegmental dysplasia which include micromelic dwarfism, disorganization of vertebral bodies, cephalocele, small orbits, mid-facial flattening, cleft palate, short neck, elongated clavicles, and alterations in the size, shape and ossification of the acromion, cora­coid process, and body of the sca­pulae. Usually present is the finding of hydroureter.

Aleck2 and others have des­cribed the less severe, although ultimately fatal form of dysseg­mental dysplasia known as the Rolland-Desbuquois variety. Most affected infants survive the neonatal period, but succumb by the age of three years. This variety of the disease has not yet been described in the Hispanic population.

Differential diagnosis

The differential diagnosis includes fibrochondrogenesis, chon­dro­­dysplasia punctata and Weissenbacher-Zweymuller syndrome.

Fibrochondrogenesis is characterized by limb and vertebral deformities including shortened dumbbell-shaped metaphyses and pear-shaped vertebral bodies3. The short limbs noted in fibro­chondrogenesis are in a proximal or rhizomelic pattern. This is in contrast to dyssegmental dysplasia which is characterized by mi­cromelia or disproportionate shortening of the entire extremity.

Chondrodysplasia punctata is typified by vertebral bodies with coronal clefts, metaphyseal splaying and stippled epiphyses. The ultra­sound diagnosis is reported elsewhere in this issue3, and the rhizomelic, potentially lethal variety has been diagnosed using radiography4.

The final diagnosis of short-limb dwarfism often requires analysis of the pathologic specimen. For example, scanning electron microscopy has been used to de­monstrate that growth plate morphology, cartilage calcification, bone morphology and collagen within resting cartilage are all more extensively abnormal in the Silverman-Handmaker form of the disease than in the Rolland-Desbuquois variety2.